The objective of this study is to access renal function in renal transplant patients. Here kidney function is determined by administering renal markers--PAH, Iothalamate and Cephalexin to renal transplant patients to study active tubular anionic secretion, filtration, and active tubular secretion. 12 kidney transplant patients will be divided into 2 groups, 6 will receive Iothalamate and PAH over a 3 hour period, the other 6 will receive Cephalexin as a bolus and studied over 8 hrs. Drugs will be assayed in plasma and urine collected, and results compared with/6 normals receiving Ioth/PAH.